It looks like Worfje and others (WinFellow site says Petter was assigned emulation core) already rewrote the Fellow custom chipset emulation in C years back, from the code remaining there is just the 68k emulator (and a few other little bits of assembler) to go. Its rewritten custom chipset emulation is STILL considerably faster than WinUAE for some chipset-heavy games on a low-end PC (e.g. Atom 1.6GHz + Windows 7, or slower).

I know WinFellow was hugely overshadowed by WinUAE, and Worfje had other commitments.
I think this would still be a worthwhile project though, if anyone with the relevant skills is willing to take it on.

Sure, next-gen high-end mobile devices will fly with UAE AGA emulation. Eventually dirt-cheap devices too.
In the meanwhile, there are still a lot of reasonably decent mobile devices (PSPs, low-end Android phones, ARM subnetbooks, etc.) which can struggle with playing Amiga 500 games in UAE, and may benefit from the faster custom chipset emulation in Fellow - which has already been converted to C!

Perhaps some 68k emulation code could be borrowed/adapted from the UAE source base to help complete this project (and maybe optimised later), to enable a cross-platform Fellow.
(Then maybe someone could draw on some XFellow code for eventual cross-platform builds.)

The last version of WinFellow to use a full assembly-based emulation core was apparently WinFellow alpha v0.4.3 build 1 (snapshot 2001/11/15). Similar to the old DOSFellow core.
This version is buggier and less compatible than the newer C-based versions (C is MUCH easier to debug and maintain!) It is also not fully compatible with Windows Vista and 7. The old builds and sources are still available though, and I agree belong in the archive. (It would be interesting to benchmark the two on old hardware for custom chipset-heavy games emulation - but the C version is still fast!)